BIO 230 PRACTICE FINAL
Services provided by ecosystems and their biodiversity that help sustain human life. Such as
pollination, water and air quality, mitigation of droughts and floods, food.
When the quality of a habitat is decreased for most but not all of the species. For example, pollution
The conversion of habitats that inhibits the use of the habitat by wildlife into land for another use,
such as farming.
Exotic or Invasive species
Species that are introduced by accident or on purpose to an area which the species never historically
A species or group of species that are unique to one area or region
The movement of nutrients within an ecosystem. Nutrient cycling is never perfect- it has inputs
and outputs. These in/outputs are small relative to the amount of nutrients within the ecosystem.
Disturbances uncouple cycling. There is a gradient from the poles to the equator.
The physical, chemical and biological transformation and movement of elements and thecycling of
nutrients within an ecosystem.
The total amount of element found within the physical or biological component of an ecosystem.
The amount of time an element spends in a pool before if leaves.
Weather and Climate
Climate is the long term trend of weather over decades for a region. Weather is the day to day
When molecules (ex. CO2 and CH4) in the atmosphere trap longwave radiation emitted from the
Earth’s surface and reemits it back to Earth, causing it to warm.
Rain that has a pH of 2.0-5.0. Caused by excess SOx, NOx, CO2. Causes damage to lakes, forests
and buildings. Biodiversity
The variety of life, including the variation of genes, species and functional traits. Includes species
richness, evenness and heterogeneity.
The break up of a continuous habitat
loss of biodiversity due to the spread of non-native generalists and the reduction of native specialists
due to the presence of non-natives.
species that are historically found in an area
a species that has a large affect on an ecosystem relative to it’s abundance.
The cycling of nutrients between ecosystems
Watershed or Catchment
A stream that drains all other streams in a terrestrial ecosystem. Can be used to measure input and
output rates of nutrients and infer how nutrients are used
The replacement of one species with another over time
Human caused. Such as increased C, S, P and N emissions and disturbances like habitat loss,
degradation and fragmentation
the directional change in climate over several decades, currently caused by anthropogenic carbon
Gases in the atmosphere that are in too high concentration compared to preindustrial levels, causing
warming of the planet.
1. Explain why some of the world’s most productive forests (tropical rain forests) can
persist on some of the world’s poorest soils.
The reason is due to the moist, damp, and humid environment, which favors faster
decomposition by decomposers and detritivores. Such that since the rate of breaking down litter
and dead matter on the forest ground into nutrients is very fast, the tree are able to absorb them;
thus, most of the nutrients is within the tree (living biomass).
Since there is a low amount of nutrients in the soil this indicates that the trees are taking them up
as soon as the nutrients are released from decompositions. Tropical rainforest is humid and warm, favouring high decomposition rates, therefore nutrient
turnover is high. Any nutrients released by decomposition is taken up by plants and is stored
in the living biomass instead of the soil. In addition, the high biodiversity can cause efficiency
in nutrient usage, since a variety of plants can specialize to use different nutrients, hence all
nutrients are taken out of the soil. Amount of nutrients in the soil gives no indication of the
cycling rate and the actual amount of nutrients within the system. Also, the heavy rainfall in
tropical rainforests cause nutrients to leach, making the soil poor.
Because the most productive forests such as tropical rain forest have a warm temperature, high
precipitation, and high moisture throughout the year, it results in high net primary production and
high rate of decomposition. Therefore, it supports high biodiversity communities including many
living plants including trees and animals. The soil is poor due to the high numbers of plants and
trees that take up nutrients faster than the soil can replenish. Due ideal abiotic conditions, plants
and animals usually grow well. Therefore, fallen leaves and animal manure can help replenish
nutrients into the system.
2. Would you expect specialist-diet or generalist-diet herbivores to be more strongly affected
by spatial patchiness of their plant prey-type(s)? Argue for ONE option only, stating
-Specialist-diet herbivores would be more strongly affected because if their plant prey is more
spatial dispersed it means that the herbivore has to use more energy in order to get to that plant;
thus, overall to gain that energy the herbivore must lose energy as well. Assumptions would be
that the plant prey are very spread a part.
- If patches are small and very spread apart the herbivore isn’t gaining any energy because the
amount it eats will be used up by the time it finds a new patch.
-Competition b/w specialist of that plant prey would make it more difficult and
increase in the usage of energy to find a “fresh” patch, which could be far away.
Assuming patches contain different amounts of the specialist’s food and that the food spread
apart in a heterogeneous landscape, the specialist diet will be more affected. Generalists can
move to any patch and eat any food so food is not limited, therefore if the space is increased
between patches, the generalist only needs a longer staying time in that patch. Whereas for
specialists, their food source can be limited within patches. Therefore if space between patches
increase, and the specialist may not have enough food in that patch to compensate the longer
travel time, causing the specialist to decrease the net gain in energy.
Specialist's diet would be more affected with the following assumption:
- patches contain a variety of food so resources that a specialist can consume are limited whereas
a generalist can intake almost all the resources that a patch provides
- the specialists are the first foragers arriving at the patch that hasn’t been grazed before. - the patch spacing is consistent and no net energy gain during travel time. Because the staying
time is shorter for a specialist is much shorter than a generalist, the distance between the patches
have to be shorter for a specialist to reach otherwise specialists won’t survive.
3. In some ways – especially by consuming only small portions of the live host/prey, rather
than killing it first – parasites on (or inside) animals are analogous to herbivores on
plants. Does this imply that parasite abundance is controlled by predation, in the manner
suggested for the control of herbivores by HSS theory? Make EITHER a “yes” OR a “no”
argument (not both), and state assumptions.
-No they are not controlled by predation because parasites need to compete with other parasites
in order to get a host to live in/on. There isn’t unlimited host supply as there is an unlimited food
supply (plants) for herbivores.
- Predation wouldn’t control there abundance because assuming no animal eats parasites as a
-Predation of herbivore with parasite would mean that the predator would now be the host for the
Assuming there is only one or a few parasite to one host so the host does not die. No, because
unlike in herbivory, which is supplied by an unlimited plant population, animal hosts are
much less abundant. Therefore, because there is a relatively less amount of food supply for
parasite compared to herbivores, parasites should be controlled by competition for a host, not by
No, they are not controlled by predation. Assuming that there is a limited amount of hosts/
animals, parasites have to compete with one another for a host to live in/on. In HSS theory, we
assume that there is nearly unlimited supplies of resources (ex. plants) for the herbivores. Plants
are unlimited for herbivores but it is not true to say animals are unlimited for parasites to live on/
in. Therefore, it is competition, not predation that controls parasites on animals.
4. Name and briefly explain three physical consequences on the world resulting from
1. There would be an increase in sea level by +25cm which consequently could mean islands
would disappear into the ocean (Maldives) and so would most sea-level areas (Richmond, New
York, London). Displacement of 1000s of people with no homes. Most of these sea-level areas
are major portsà economic consequences
2. Increase frequency of extreme events such as heat wave, heavy rain, increased droughts,
increase in hurricanes, floods, and forest fires. Consequently these damages would have
immense impact of the economy, on the ecosystem ( frequently being disturbed → not enough
time to mend the damages), and increase in deaths. 3. There would be 3 degree increased in temp at the equator and a 5-8 degree increase in temp at
the poles. Increase in temp at the poles would cause increase amount of glacial melting; thus, an
increase of sea levels and decreases glacial surface areas which means less hunting ground for
polar bears. Also warmer temps in water could cause a decrease in fish population (trout, salmon,
etc.) b/c they require cold water to survive.
1. Global temperatures will increase as greenhouse gases warm the planet. Temperature is project to
increase 3C in the tropics, 5-8C at the poles and globally, 1.8-4C.
2. Increased sea levels due to melting of polar ice caps. It is projected that there will be 25 cm
increase in sea level by 2100. Many places below sea level, like the Maldives, Richmond or
Baghdad will be submerged.
3. Animals and plants are affected as well. In some areas, causes earlier spring green, earlier bird
migrations, death of 4% of lizard species and projected that 20% decrease by 2050.
1. Rise in sea level: due to the increase in temperature, the glaciers and ice caps are melting causing
the sea level to rise.
2. Global temperature increase: due to increase in greenhouse gases produced through industrial
activities, burning fossil fuels and increase in CO2 emission.
3. Animal responses: results in habitat loss, fisheries decline, range change (dispersal), change in
time for migration, breeding season.
5. Briefly explain (a diagram could help) why tropical forest vegetation may be more
vulnerable to climate warming than boreal forest vegetation
In temperature increases, respiration will be favoured in the Tropics (ie. when respiration is above
photosynthesis). Respiration causes a net loss in energy in plants, therefore if plants switched to
respiration for a prolonged period, they will die. However, if temperatures increased, Boreal forests
would still favour photosynthesis, therefore will be less
Note: my answer is completely different... and I feel like I’m off... your explanation makes
sense The decomposition rate and nutrient cycling is going to be faster the the climate is warming.
Due to the location, abiotic factors of the tropical forests, the soil temperature is warmer
here than boreal forests. The mean residence time for tropic is going to be even faster
than before, especially the time for nutrients like nitrogen and phosphorus is so much lower
compared with boreal forests. Climate warming will act on boreal forests eventually but just
much slower than it will act on tropical forests due to its already fast rate of decomposition.
- Tropical forest vegetation would be more vulnerable due to as temperatures increase the
rate of photosynthesis decreases thus, the rate of respiration increases. If the temperature
increases to a very high amount and extended amount of respiration could cause tissue
deterioration of the plant and potential death of plants. In addition, as temperatures
increase the amount of moisture would decrease consequently. Without enough moisture
(water) plants would not be able to photosynthesize properly.
6. Explain briefly how diet-switching by a foraging animal population could relate to prey
diversity (and/or biodiversity) in the area occupied by that forager-population; your answer
an understanding of frequency-dependent selection.
Forager switching can cause higher biodiversity because foragers that are non-selective will eat
whatever prey is at highest density (frequency dependent selection). By doing this, the population of
prey species on which it feeds will be kept under control so no one species dominates other species,
thus promoting coexistence and increases biodiversity. A foraging animal switches diet because they discover accidentally that their diet allows a new kind
of prey and it’s high in density. A foraging animal controls the prey density and by diet-switching, it
doesn’t drive the prey before diet-switching to extinction. Therefore, it increases biodiversity.
-Diet switching is a frequency dependent predation because the foraging animal prefers consumes
the most abundant/common prey. Thus the foraging animal increases its preference for a prey as the
prey becomes more abundant.
- It relates to prey diversity because a foraging animal does not have a specific diet; thus, it will eat
prey that is more common at that time and will switch its diet as that prey’s density becomes low.
In other words, the forager does not eat the prey population until extinction. By diet-switching it
reduces the chances of one population to be eaten until extinction; thus, increasing the biodiversity.
7. Some prey animals (like our old lab friends, terrestrial isopods) are largely protected
from predation because they secrete in their tissues bad-tasting, mildly-poisonous
chemical compounds... but this has not allowed them to breed uncontrollably and become
superabundant, so the benefit of protection must also have a cost. Suggest ONE specific cost
of this protection-bytoxicity benefit; state your cost-idea in the form of a testable hypothesis
deriving from theory, and state assumptions.
Assuming energy resources are limited for isopods, isopods allocate their energy towards producing
the toxins, leaving very little energy left for reproduction.
The energy invested in isopods focuses more on producing toxins than on reproduction. If we
assume energy usage is very limited for the isopods, then isopods will not have energy to reproduce
once they invest and use most of energy on toxin production.
- Terrestrial isopods use the majority of their energy towards protecting themselves (producing
poisonous toxins) and not enough energy is devoted for reproductive purposes.
- Assuming that the isopods only have a limited amount of energy that they only use towards
protecting themselves and for reproduction.
8. Some predators (such as baleen whales, and web-building spiders) exhibit a style of prey-
capture behaviour known as a Type 1 functional response (as illustrated in the graph at left).
a. Describe in biological (not mathematical) terms the behaviour of a Type 1 forager as shown
on the graph. (5 marks)
The forager is non-selecting, meaning the feeding happens at a rate proportional to the amount of
prey available. Eventually levels off because the feeder reaches maximum feeding capacity (ie. it
cannot eat any faster or any larger amount at this point) Predators exhibit typical filter-feeder. As the prey density (N) increases, the number of prey caught
in a given period of time increases until it reaches a certain N that the graph just levels off. The
leveling-off happens when the feeding capacity reaches maximum.
- The number of prey caught in a certain amount of time (Ne) increases as the prey density in the
area (ex. Filter feeders mouth) increases. As the graph plateaus it indicates that the filter feeder has
reached the maximum it can capture/ eat and thus it reaches its maximum capacity (its gills become
clogged and can no longer capture anymore plankton) and swallows. Once the filter feeder swallows
if starts back at zero.
-Whatever was caught does not reflect the filter feeders hunting skills… It reflects the richness of the
b. In any type of functional response (Types 1, 2, or 3), there is always a “plateau” number of
prey caught when N is high; why? (5 marks
Plateaus because the forager has a limit to the amount it can eat (ie. it becomes full).Even though the
number of prey increases, foragers cannot continue to feed at a rate porportional to the amount of
prey because it cannot catch/consume the prey at a faster rate. The situation shifts from forager being
limited to amount of prey, to forager being limited by the amount the predator can catch/eat
Because there is only so much that the predator can consume, there is a limit to its feeding capacity.
Even when the prey density increases, the predator’s ability and maximum capacity for consumption
of resources don’t change.
- The plateau indicates the maximum capacity the organism can consume. This is the point where the
organism can no longer take in more / too full to eat.
-Even with the increase density of prey the predator cannot eat anymore b/c it has reached its
9. One proposed explanation of high species-richness in the Tropics compared to other areas of
the Earth is the “Productivity Hypothesis”.
a. describe briefly the mechanism by which the Productivity Hypothesis is supposed to work (4
Productivity hypothesis states that because the tropics have high productivity, it also has high
diversity of food and species will specialize to eat the food, causing speciation and higher
biodiveristy. Higher productivity also leads to increased coexistance because there is less
competition for food and decreased extinction rates, causing high biodiversity.
Productivity hypothesis suggests that there is a high species richness and high productivity in the
tropics that support diverse communities because of its pleasant conditions for growth and survival
throughout the year. Plants are productive, as are the organisms consuming them so plenty of food for all consumers in food web, therefore, it promotes coevolution while keeping biodiversity high.
- Productivity hypothesis is an ecological mechanism. Such that areas, like the tropics, have good
producing conditions (high rainfall); thus, have a high level of productivity (growth of plants) for
consumers to eat. There is enough for new species to immigrate into these areas as well maintain
the species richness that it already has (extinction rate is low). There is enough vegetation for lots of
species to eat.
b. is the Productivity Hypothesis a deterministic or a stochastic theory? Select ONE choice,
and justify (6 marks).
It is deterministic because ecological principles state that with large amounts of food source,
competition decreases to allow coexistance. Also. species will partition resources to avoid niche
overlap by the competitive exclusion principle, therefore causing speciation. All these events,
although not always inevitable in all ecosystems, can be a consequence of high productivity. The
productivity hypothesis never mentions any events that can be stochastic, such as disturbances and
the climate of the tropics is stable.
It is deterministic because the climate and conditions don’t usually change or fluctuate much, it is
determined for that particular area. Because productivity is high, it has plenty of food for consumers
in food web, leading to decrease in competition, increase in coexistence and high species richness:
- predators become diverse and numerous, keeping the prey abundance low. Species held down to
low densities are unlikely to be driven to extinction by competition or
- predators can persist even if they are specialized because food supply is steady, leading to diverse
predators with little niche overlap are unlikely to be driven to extinction by competition
It is deterministic theory because the abiotic factors that influence high productivity (enough
vegetation for consumers to eat and immigration of new species into the area) is not due to random
chance.Abiotic factors such as temperature and rainfall are determined by where the area is located
in the world (areas near the pole would have low productivity). The coexistence of new species and
existing ones are determined due to the high productivity of vegetation; thus, species may not have
overlapping niches and would not be driven to extinction due to intense competition against species
10. In order to avoid constructing an expensive addition to a city’s wastewater treatment
plant, a city engineer suggests that after removing suspended solids and noxious chemicals,
the wastewater could be spread on a scrub forest and permanently solve two major problems.
He reasoned that the remaining organic matter in the wastewater would be broken down by
decomposers (e.g. soil fungi and bacteria), and excess inorganic nutrients would be taken up
by forest plants, thereby preventing eutrophication (i.e. overfertilizing) of a stream which
currently received the nutrients. Aside from aesthetic considerations, where has the engineer gone wrong in his thinking? (10 marks)
-overfertilization of terrestrial ecosystem
-terrestial forest cycling could also be saturated therefore further inputs of nutrients might exceed
the rate of cycling, therefore causing these elements to turn into compouds like N2O, CO2 or CH4,
which are greenhouse gases
-Plants can’t take up inorganic nutrients- they must be turned into usable forms first
-decomposition and cycling rates might not be able to keep up with the rate of our input
-if decomp/cycling rate cannot be kept up with, then there will be nutrients in runoff and
eutrophication of aquatic ecosystems
-the process of adding waste water to forests could cause disturbances, which uncouples nutrient
-plants might be adapted to low nutrient levels, so if you increaes nutrient levels these plants may be
-can cause acidification in the case of excess N deposition
-does not consider what will happen to wildlife habitat
- Plants do not take up inorganic nutrients, these nutrients needs to be broken up in order for the
plants to absorb them
-Also, if the engineer was planning to dump the organic matter in the wastewater in a random forest
without considering decomposition rate it could cause problems. Decomposition may not be ideal in
that particular area; thus, there would be an accumulation of this matter that cannot be broken down
for plants to absorb. In addition, if that forest is already high in nutrients in both the soil and in the
living biomass, the inorganic/organic matter would accumulate and possibly seep through the soils
into ground-waters (aquifers) and cause eutrophication of a stream.
-The inorganic nutrients could possibly still be harmful to organisms and plants. Example excess
sulfur and nitrogen in high concentration would be harmful for living life-forms. If these inorganic
nutrients seeped into underground waters could be harmful to marine organisms (fish).
11. Suppose that a “pulse” of nutrients was added to a lake in each of two consecutive years. In
both years, measurements of nutrient pool sizes in the phytoplankton, herbivores, predators
and detritivores were made 1 week before and 1 week after the pulse. Offer an explanation
for the following observations made one week after the pulse was added (note: “increase”,
“decrease”, and “no change” refer to the observed changes compared to the pre-pulse
conditions for that particular year):
• Year 1: phytoplankton and detritivores both increase, but no change in herbivores and
• Year 2: Phytoplankton and herbivores both decrease, but predators and detritivores both
Originally, the prey density (phytoplan